package main

type tokenKind int

func (k tokenKind) String() string {
	switch k {
	case plusEquals:
		return "+="
	case plus:
		return "+"
	case minusEquals:
		return "-="
	case minus:
		return "-"
	case starEquals:
		return "*="
	case star:
		return "*"
	case slashEquals:
		return "/="
	case slash:
		return "/"
	case lparen:
		return "("
	case rparen:
		return ")"
	case lbracket:
		return "["
	case rbracket:
		return "]"
	case lbrace:
		return "{"
	case rbrace:
		return "}"
	case comma:
		return ","
	case dot:
		return "."
	case colon:
		return ":"
	case semicolon:
		return ";"
	case doubleEquals:
		return "=="
	case equals:
		return "="
	case bangEquals:
		return "!="
	case bang:
		return "!"
	case tildeEquals:
		return "~="
	case tilde:
		return "~"
	case caretEquals:
		return "^="
	case caret:
		return "^"
	case doubleAmpersand:
		return "&&"
	case ampersandEquals:
		return "&="
	case ampersand:
		return "&"
	case doublePipe:
		return "||"
	case pipeEquals:
		return "|="
	case pipe:
		return "|"
	case doubleLangleEquals:
		return "<<="
	case doubleLangle:
		return "<<"
	case langleEquals:
		return "<="
	case langle:
		return "<"
	case doubleRangleEquals:
		return ">>="
	case doubleRangle:
		return ">>"
	case rangleEquals:
		return ">="
	case rangle:
		return ">"
	case identifier:
		return "identifier"
	case str:
		return "string"
	case number:
		return "number"
	case export:
		return "export"
	case function:
		return "func"
	case ret:
		return "return"
	}

	return "invalid token"
}

const (
	none tokenKind = iota
	plusEquals
	plus
	minusEquals
	minus
	starEquals
	star
	slashEquals
	slash
	lparen
	rparen
	lbracket
	rbracket
	lbrace
	rbrace
	comma
	dot
	colon
	semicolon
	doubleEquals
	equals
	bangEquals
	bang
	tildeEquals
	tilde
	caretEquals
	caret
	doubleAmpersand
	ampersandEquals
	ampersand
	doublePipe
	pipeEquals
	pipe
	doubleLangleEquals
	doubleLangle
	langleEquals
	langle
	doubleRangleEquals
	doubleRangle
	rangleEquals
	rangle
	identifier
	str
	number
	export
	function
	ret
)

type token struct {
	kind  tokenKind
	value string
	line  int
}

func (t token) String() string {
	if t.value != "" {
		return t.kind.String() + " " + t.value
	} else {
		return t.kind.String()
	}
}

type tokens struct {
	src   <-chan token
	toks  []token
	index int
}